Fluorescent lamp circuit



lApril 2\0, 1948. R. w. KEISER ETAI. 2,439,975

FLUORESCENT LAMP CIRCUIT 'Filed Aug. 5, 1942 2 Sheets-Sheet 2 [TUDE nuunnnnunauuu E111/UMS R ULSSQB LO RlsP/r. mche bww Patented Apr. 20, 1948 FLUORESCENT LAMP CIRCUIT Russell W. Keser and Charles Philippe Boucher, Fostoria, Ohio, assignors to Boucher and Keiser Company, Atlanta, Ga., a partnership Application August 5, 1942, Serial No. 453,714 2 Claims. `(Cl. 315-280) This invention relates to fluorescent lamps and, more particularly, to starting and operating circuits for such lamps.

It is the general object of the present invention to provide novel and improved starting circuits and associated -apparatus for use in conjunction with one or more fluorescent lamps.

More particularly it is an object of the invention to provide circuits which operate automatically on closing of the line switch to rst provide a potential for striking an arc in each of the lamps, associated with the circuit, by the cold cathode starting method and to subsequently reduce the voltage applied to the lamps to that most desirable for their continued operation and long life.

It is an important object of the invention to provide circuits for iluorescent lamps which provide substantially instantaneous lighting of the same upon the closing of the line switch and which automatically provide both the necessary striking potential for igniting the lamps and the reduced operating potential for delivering maximum life and light intensity.

A further object of the invention consists in the provision of accessories for incorporation into the starting and lighting circuits for fluorescent lamps, which use a minimum amount of copper and magnetic material commensurate with the supplied operating voltage and current.

A still further object of the invention consists in the provision of starting and operating circuits and accessories which provide not only a superior current wave form whereby maximum light is obtained from the lamps but which give substantially identical wave form to the current owing to both the leading and lagging lamps of a pair.

One of the important features of the invention resides in the construction and operation of the switch which automatically changes the higher starting voltage to the lower operating voltage following the striking of the arcs in the lamps, and which, subsequent to the extinguish- 'ing of the lamps by the opening of the line switch,

conditions the circuit for instantaneous starting of the lamps when' the line switch is reclosed.

Other and further objects and features of the invention will be more apparent to those skilled in the art upon a consideration of the accompanying drawings and following specification wherein are disclosed several exemplary embodiments of the invention with the understanding that such changes therein, modiiications thereof, and combinations of the same may be made as fall within the scope of the appended claims Without departing from the spirit of the invention. i

In said drawing: v

Figure 1 is a schematic and diagrammatic showing of the circuit and accessories arranged be tweenasource of alternating current and a pair of fluorescent lamps requiring a different operf ating voltage than the source;

Figure 2 is a view similar to Figure 1 but showing a circuit providing less radio interference;

Figure 3 is a showing of another circuit modication;

Figure 4 shows a further circuit modification;

Figure 5 illustrates current curve wave forms in two lamps operated from prior art devices; and

Figure is a viewsimilar to Figure 5 but showing curves taken `when using circuits and apparatus of the present invention.-

There are commercially available at the present time two general systems for the starting of fluorescent lamps. The first of these systems, known asthe hot cathode method, is the one most commonly used. It requires lamps having filaments at each end and some circuit arrangement which /iirst supplies current to heat the filaments and then provides a shock voltage to break down the ionized gas between the iilaments and strike and maintain the arc. The apparatus includes, in addition to a transformer if required, a ballast or reactance for each lamp and a so-called starter switch for each lamp which serves to connect the iilaments thereof to the power source and to disconnect them after they have been heated. This system has a number of disadvantages, not the least among which is the slowness of the starting, from ten to forty-five seconds elapsing after the closing of the line switch before the lamps are properly burning. Furthermore, if a number of lamps are controlled by a single line switch they do not all light simultaneously.

A system of instantaneous starting is the second known form and actuates the lamps on the so-called cold cathode principle. Because lamps with filaments acting as the main electrodes are the only types readilyV available, these are used in this system also but the two terminals of each lament are connected together to increase the life of the same.

4For starting, a relatively high potential must A be applied between the electrodes of each lamp to break down the resistance of the gas column therein, but this high potential is not needed for operation and is, in fact, detrimental to the lamp life. If the actuating transformer is designed to supply the high striking voltage and relies on poor regulation to reduce this voltage to that approximating the desirable operating voltage, then high copper losses obtain and poor wave form results. This system also builds up an unnecessarily high voltage across the terminals of the main condenser used with one lamp of a pair to improve the power factor and lessen the stroboscopic effect. This, in connection with the necessary tem of lighting uorescent lamps in accordance with the present invention, is illustrated in Figure 1, wherein the source of alternating-current is indicated at I0, connected,thronghalneswitch II to the primary I2 of a transformer .l33,.shown such as argon, neon or the like. A glow elec- ,.trodeAU is arranged within 4tha-switch envelope .and kconnectediby conductor 14| tosome point such as 42 on the transformer which has a differ- '.5 ent potential than that to which the bimetallic i strip 39 is connected. This difference in potential rbetween239 and 40 causes a glow in the ionizable lmedumfassisted by v`a suitable deposit of emis- .sivamaterialnlthe bimetallic arm 39 it necesin this embodiment as of the auto'etransiormer vl0 sary, whichfheatsthe bimetallic element causing type although this form is notnecessaryand may not be desirable under certain "conditionsasewill be later pointed out. The circuit is stiowniorY the usual arrangement-:fof lighting two lamps I4 .and I5 lfrom one,sethraocessories. The lilamentary electrodes L |56 Loieach 'ofi thesejlaxnps. are short-circuited as shown"to,provide"for a single connection at eachendof eachlarr 1p. LThe right hand ends ofthe twoflamps are connected by the conductor-|`8-`to`the lefthand end "|19 of the primary I2. The'leithand endoflamplI-II is connected by conductor to one end ofthefreactor `-2| whiletheleithanden'd-of lamp 515 is connected by the conductor-Z2 Atosone-endfof reactorV 23, the condenser 12'4 ybein-g interposed Yin this ,circuit in the usualmanner to improve the power factor. The remaining-endsoflthe ftwo' reactors f2 I and '23 hare-connected `togetherby :wire and thence by wire-ZBf to righthan'dend 12J Vvoi? the rsecondary` of theitransformen The connectionsjust described; provideLthenor- 4mal operating f circuit 'Si or fthelamps wherebyfthe desired operating potential iis applied nto seach lamp by reason of'theturns zratocof :thetwo it to move contact out of engagement with "contact 33andopen the circuit to the booster coils thereby conditioning the system for normal operation. The glow discharge, which consumes 15 a very small amount ofcurrent, continues during Vthe, normal operation of.'the vlamps'to insure'deenergization of the'boostcr coils.

In order to limit the "movement of the @bimetallic arm "39 Vunder the continuous' heating 20 of the"glow,"to thus prevent it frcmbecoming permanently "distorted and unable to return the contacts Lto. closed circuit position, the electrode liis madesufliciently rigid andiprovided with an insulating stop43 as shown. This limits .the

25 movement of contact 35 to rjust slightly more than necessary to open circuitfwith 33.

LIf desired, aresistor 45 may "be .inserted in conductor 3| 'to control the starting current. 'This Vis in circuit for lsuch .a short time that '-30 lossesthere'from 'arancgligible windings of .the `transformer .and the current Y-35 'each "lamp-maybe 4arranged Aon separate cores.

limited by the predetermined :reactances sofithe reactors i2-I Vand 23 an'dithefcondenserizll.

:In order .to provide the highier :voltage :necessaryior starting-theflamps, eachreactorhasas- Furthermore, lan additional number of reactors andibooster `coils mighttbe used-where'it is de sirable'to'controhmorethan two 'lamps at one time. The reactorswill-preferablyv beV constructed sociated therewith and woundmnzthe samecorea 'in accordance lwith the disclosure in the -cocoil :28, 29, respectively. `These: coils lmayibe connectedeither in iseries lor, .'ashown, `in parallel and :energizedifrom .la portinnso'f the f,secondary .winding of the auto :transformen .The ,size .of `this Yportion is selected :iin :accordance ==with the 1turnst-ratiolbetween the .-reactorf and .its xhoest-,ing

coil to :provideithefdesired. startinggmtential.

-In this connection it V,may lie-.noted that each reactorsand its boosterfcoilcanrbeconsidered. asa A,transforirler in1whichntheeboostertcoil as primary induces -asuperimposed lfvoltagge on thaty already existing in the Secondary. The :conductor V3|) associating one end of #,eaclmof 4.the two booster coils, is connectedxtolconductonz. .Theother len ds of the "booster coils areconnected .together :and to conductor@ .whichleadstothefstationary contact 33 in an 7automatic .switch `'shown .inclosed-in the .evacuated andgas-filled envelope 34. A second contact 35 is under Inmcurrent conditionsin engagementwith contact33to close the circuit through .wire 36 utotap 31,on".the auto transformer. The condition.justedescribed-is'that Yfor ystarting `for now .the .booster coils are energized from thesection-between 2`1 and31 on "the transformerv and ,increase 'the ,voltage in `each .of

=thereactor.circuits tocause-me striking of the arcs in thelamps.

I t is not desired to `maintain ithe striking'voltage except momentarily, so delay racting 4means areprovided, actuated bycurrent How, to open thecontacts of the automatic switch.

Contact35v is mountedona bimetallic'arm'39 so arranged that, upon heating of this arm, the

contactswill be;disengaged. The-envelope has y '75 In `ligure *3 is illustrated -a tfurther modicaan appreciable content'of anlionzaiblemedium,

'pending application Nof y'Russell W. AReiser, Serial No. "421,700, v:filed December 4, 1941, for Reactances, whichfissued August 14, 1945, as United-States Patent Number 2,382,012. Here are shown'rnultiple currentjdividing reactors inif V"foundunnecessary-and their use can be oblviated even in the `presence vof 'radio receiving equipment f-'by vresorting vto `a circuit such as illustrated in AFigure V2. The major portion of this -1circuit, :particularly yas yregards the reactor,

booster "coils V'and Vautomatic switch is identical with that in iFigure 1 and will not be further described. Theitransformerfhowcver, is modi- 'icd-byseparating-'thewindings into three parts. Theprimaryf-E is an entirely independent Winding `andfis-eonnected'only to the source of power supply V 'through the line switch. `The secondary 5l is-directlyconnected-with only Athe lamps and the xrea-chir coils :2| and 23 Vwhile the tertiary windingf'zi on fthetrans'former provides the nec- `7`0 essary tvoltage Tor the'booster coils 28 and 23,

its voltage :being yapplied thereto through the medium of an 'automatic switchas previously described. The complete electrical separation of thethree v-coils :avoids any radio interference.

tion in which the primary 54 of the transformer is associated in the manner of an auto transformer with the secondary 55. The' connections from these parts to the reactors and lamps being as shown in Figure 1. The tertiary winding 56 is arranged to be connected to the booster coils 51 and 58 in the manner already described except that these coils instead of being connected in parallel with each other are arranged for a series connection.

In Figure 4 a separate primary coil 60 is illustrated while the secondary is divided into several parts. applied to the lamps by the leads 6I and 62. The reactors and their booster coils are arranged in a complete series relationship, the reactors 63 and 64 being at the ends and the booster coils 65 and 66 in the center. The leading lamp is operated from 6l and 62 through only the reactor 63 while the lagging lamp derives its operating potential between 6l and 62 and the three windings 64, 65 and 66, the total reactance of which is proper to provide the desired operating potential and current limitation.

For starting purposes an automatic switch connects an additional potential from the taps on the secondary of the transformer by way of the conductors 62 and 68 through the booster windings in series. A resistor 69 is interposed in this circuit to limit the starting current. It Will be noted that in this embodiment only, the reactor-booster coil combination is of the auto transformer type as distinguished from the arrangement within other embodiments. This embodiment makes the maximum use of the copper and iron in the accessories since all the coils are always in use.

It has been ascertained that a greater quantity of light can be obtained from the fluorescent material which is activated by the arc burning in the lamp tube as the current curve thereof approaches a sine wave. The type of wave illustrated in the two views of Figure 5 represents one of the better forms obtained by oscillograph records from ballast equipment for fluorescent lamps now available on the market. The top view in that gure represents the curve of current flow in the lamp column of the lagging lamp of a pair, whereas the lower figure illustrates the current in the leading lamp. The upper curve is not too bad and will produce Very good light but the lower curve is such as to reduce the total illumination per ampere from the lamp whereby low efficiency is obtained. Because of the symmetry of applicants equipment, the superior form of curves illustrated in Figure 6 are obtainable. lt will be noted that there is but little difference in the curves for the lagging and the leading lamps. There is also a minimum of third harmonic which is recognized as a serious disturbing factor in producing good illumination. It also has detrimental effect on adjacent radio equipment.

Any of the circuits shown with independent transformer primaries may be used without the small lamp shunting condensers, since the separation of primary and hence power line from any irregularities in the secondary eliminates any chance of radio interference.

It will be obvious to those skilled in the art that the transformers of any oi the above cir- The whole of the potential thereof isV cuits can be designed or connected for use with various line potentials both higher or lower than those needed by the lamps. In fact the transformers can be entirely eliminated where the line voltage supplies the correct potential for normal lamp operation. Under these conditions the booster coils are merely energized direct from the line.

Having thus descri-bed the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A starting and operating circuit for a fluorescent lamp comprising a current source, a voltage step-up transformer at least a portion of the winding of which is connected in series with said lamp across the said source, a switch to temporarily connect the primary of said transformer across said source to impress a high voltage across said lamp during the starting period, at least a portion of the transformer winding serving as a ballast for the lamp during operation thereof, said switch comprising a pair of contacts supported in normal engagement, a bimetallic support for one of said contacts, and means to heat said support to cause it to separate said contacts, said heating means being energized continuously from said current source only during the operation of the lamp.

2. An instantaneous lighting circuit for fluorescent lamps including in combination a source of alternating current, a step-up transformer connected to the source through a line switch, a lamp and reactor in series continuously so connected to said transformer as to supply appropriate potential and current for normal lamp operation, a booster coil inductively related to the said reactor, a normally closed switch through which said booster coil is connected to said transformer so as to increase the potential in the lamp circuit to that necessary for instantaneous starting of the lamp by the cold cathode method, said. normally closed switch including a contact supported by a bimetallic element, and current actuated means to continuously heat said element upon the closure of the line switch.

CHARLES PHILIPPE BOUCHER. RUSSELL W. KEISER.

REFERENCES CITED The following references are of record in the le of this patent:

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